it is known that the viscosity index of an oleaginous composition such as lubricating oil can be increased or improved by incorporating therein certain polymeric materials which function as viscosity index improvers. Known viscosity index improvers include polyisobutene and copolymers of ethylene and other hydrocarbon olefins. It is also known that these viscosity index improvers can be grafted with grafting materials such as, for example, maleic anhydride and the grafted material then reacted with a polyamine or polyol to form multifunctional viscosity index improvers.
Generally, the polymeric materials useful as viscosity index improvers are those having number average molecular weights of from about 15,000 to about 250,000, preferably from about 20,000 to about 150,000. However, some polymers having this molecular weight range are difficult to process, isolate and handle, or are relatively more expensive to produce than their higher molecular weight homologs. Therefore, with such polymers it is generally easier and more economical to form their higher molecular weight homologs, for example those having number average molecular weights of from about 30,000 to about 500,000, and then to degrade these high molecular weight polymers to the desired molecular weight.
It is known that olefin and di-olefin homopolymers and ethylene-.alpha.-olefin copolymers may be degraded, thereby reducing the molecular weight thereof. Such degradation is known to be accomplished, for example, by shear assisted oxidation of the polymers and copolymers in air in a mechanical mixer, such as in an extruder, masticator, Banbury mixer, rubber mill, or the like, and by heating the polymers and copolymers, sometimes in the presence of air. One such degradation process, which is described in U.S. Pat. No. 3,313,793, involves (a) the formation of a solution of a conjugated diene polymer, (b) combining therewith a peroxide and a copper source such as copper, a copper halide or a copper carboxylate, (c) heating the resulting mixture in the substantial absence of oxygen, and (d) recovering a diene polymer product having a substantially reduced average molecular weight.
U.S. Pat. No. 3,332,926 relates to the thermal degradation of polyolefins, including ethylene-propylene copolymers, to produce relatively low molecular weight polymers which are useful, for example, as wax substitutes, blending agents, coating compositions and, in general, in fields where hydrocarbon resins and waxes find utility. The process described in that patent comprises mixing a crystalline starting polymer with from 0.075% to 10% by weight of a metal salt of carboxylic acid and heating the mixture in an atmosphere which is substantially free from oxygen to a temperature of about 275.degree. C. to 450.degree. C., until a substantial reduction in the molecular weight of the polymer takes place.
U.S. Pat. No. 3,316,177 discloses a functional fluid containing a sludge inhibiting detergent comprising the polyamine salts of the reaction product of the maleic anhydride and an oxidized interpolymer of propylene and ethylene. The interpolymers from which the oxidized, degraded interpolymers are derived usually have molecular weights of at least about 50,000. The interpolymers are oxidized and degraded by heating them at a temperature of at least about 100.degree. C. in the presence of oxygen or air. Such degradation usually is characterized by a substantial reduction of the molecular weight of the interpolymer.
U.S. Pat. No. 3,345,352 relates to a catalytic process for the thermal degradation of the polyolefins, including copolymers of ethylene and propylene. The degradation process involves heating a mixture of a crystalline polyolefin and an oxide or carbonate of an alkali metal, alkaline earth metal, or certain selected transition metals such as copper, iron, titanium, vanadium, etc. in an atmosphere substantially free of oxygen to a temperature of from 275.degree. C. to 450.degree. C. for a minimum time period of at least five minutes.
U.S. Pat. No. 3,687,849 relates to lubricants containing oil-soluble graft polymers derived from degraded ethylene-propylene interpolymers. The interpolymers from which the degraded polymers are derived usually have a molecular weight of about 50,000-800,000, and the degraded interpolymers are prepared by heating the interpolymer, or a fluid solution of such interpolymer, in an inert solvent, at a temperature of at least about 140.degree. C. in the presence of oxygen or air. The degradation of the interpolymer is characterized by a substantial reduction of its molecular weight. A similar disclosure is set forth in U.S. Pat. No. 3,687,905.
U.S. Pat. No. 3,769,216 relates to polymers which are produced by reacting a primary or secondary amine and a mechanically degraded, oxidized atactic ethylene propylene copolymer, and to automotive lubricating oils containing such polymers as antivarnish additives. The ethylene propylene copolymer is mechanically degraded in the presence of oxygen and in the absence of any solvent in a closed vessel equipped with shearing blades. A typical apparatus of this type is described as a device containing counter-rotating helical blades and known as a "Brabender Torque Rheometer."
U.S. Pat. No. 4,089,794 discloses ethylene copolymers derived from about 2 to 98 wt % ethylene, and one or more C.sub.3 to C.sub.28 .alpha.-olefins, for example ethylene-propylene, which are solution-grafted with an ethylenically unsaturated carboxylic acid material, and thereafter reacted with a polyfunctional material reactive with carboxyl groups. The resulting polymers are useful as dispersant additives for lubricating oils and hydrocarbon fuels, and as multifunctional viscosity index improvers if their molecular weight is above 10,000.
U.S. Pat. No. 4,113,636 discloses the mechanical degradation at elevated temperatures, and in the presence of air or oxygen-containing gas, of copolymers comprising about 68 to 80 mole ethylene and one or more C.sub.3 -C.sub.8 .alpha.-olefins to form an oxygenated-degraded polymer which is then reacted with an amine compound. The resulting aminated polymers are useful as viscosity index improving additives.
U.S. Pat. Nos. 4,074,033 and 4,201,732 relate to a process for improving the processability for high molecular weight neoprene polymers. The process comprises treating a solution of the polymers in an organic solvent with an organic peroxide, in the presence of oxygen, to reduce the molecular weight of the neoprene and to lower the viscosity of the solution. The process may be conducted at room temperature with or without agitation, and an accelerator such as a cobalt salt or other transition metal salt may be employed.
The concept of grafting high molecular weight ethylene and .alpha.-olefin copolymers, either degraded or undegraded, with acid moieties such as maleic anhydride, followed by reaction with an amine to form a composition useful as a multifunctional viscosity index improver, e.g., viscosity index improver-dispersant, oil additive is also known and in addition to being disclosed in some of the aforediscussed patents is also disclosed, inter alia, in the following disclosures:
U.S. Pat. No. 3,316,177 teaches ethylene copolymers such as ethylene-propylene, or ethylene-propylene-diene, which are heated to elevated temperatures in the presence of oxygen so as to oxidize the polymer and cause its reaction with maleic anhydride which is present during the oxidation. The resulting polymer can then be reacted with alkylene polyamines.
U.S. Pat. No. 3,326,804 teaches reacting ethylene copolymers with oxygen or ozone, to form a hydroperoxidized polymer, which is grafted with maleic anhydride followed by reaction with polyalkylene polyamines.
U.S. Pat. No. 4,089,794 teaches grafting the ethylene copolymer with maleic anhydride using peroxide in a lubricating oil solution, wherein the grafting is preferably carried out under nitrogen, followed by reaction with polyamine.
U.S. Pat. No. 4,137,185 teaches reacting C.sub.1 to C.sub.30 mono carboxylic acid anhydrides, and dicarboxylic anhydrides, such as acetic anhydride, succinic anhydride, etc. with an ethylene copolymer reacted with maleic anhydride and a polyalkylene polyamine to inhibit cross linking and viscosity increase due to further reaction of any primary amine groups which were initially unreacted.
U.S. Pat. Nos. 4,144,181 is similar to 4,137,185 in that it teaches using a sulfonic acid to inactivate the remaining primary amine groups when a maleic anhydride grafted ethylene-propylene copolymer is reacted with a polyamine.
U.S. Pat. No. 4,169,063 reacts an ethylene copolymer in the absence of oxygen and chlorine at temperatures of 150.degree. to 250.degree. C. with maleic anhydride followed by reaction with polyamine.
A number of prior disclosures teach avoiding the use of polyamine having two primary amine groups to thereby reduce cross-linking problems which become more of a problem as the number of amine moieties added to the polymer molecule is increased in order to increase dispersancy.
German Published Application No. P3025274.5 teaches an ethylene copolymer reacted with maleic anhydride in oil using a long chain alkyl hetero or oxygen containing amine.
U.S. Pat. No. 4,132,661 grafts ethylene copolymer, using peroxide and/or air blowing, with maleic anhydride and then reacts with primary-tertiary diamine.
U.S. Pat. No. 4,160,739 teaches an ethylene copolymer which is grafted, using a free radical technique, with alternating maleic anhydride and a second polymerizable monomer such as methacrylic acid, which materials are reacted with an amine having a single primary, or a single secondary, amine group.
U.S. Pat. No. 4,171,273 reacts an ethylene copolymer with maleic anhydride in the presence of a free radical initiator and then with mixtures of C.sub.4 to C.sub.12 n-alcohol and amine such as N-aminopropylmorpholine or dimethylamino propyl amine to form a V.I.-dispersant-pour depressant additive.
U.S. Pat. No. 4,219,432 teaches maleic anhydride grafted ethylene copolymer reacted with a mixture of an amine having only one primary group together with a second amine having two or more primary groups.
German published application No. 2753569.9 shows an ethylene copolymer reacted with maleic anhydride by a free-radical technique and then reacted with an amine having a single primary group.
German published application No. 2845288 grafts maleic anhydride on an ethylene-propylene copolymer by thermal grafting at high temperatures and then reacts with amine having one primary group.
French published application No. 2423530 grafts maleic anhydride on an ethylene-propylene copolymer with maleic anhydride at 150.degree. to 210.degree. C. followed by reaction with an amine having one primary or secondary group.
The early patents such as U.S. Pat. Nos. 3,316,177 and 3,326,804 taught the general concept of grafting an ethylene-propylene copolymer with maleic anhydride and then reacting with a polyalkylene polyamine such as polyethylene amines. Subsequently, U.S. Pat. No. 4,089,794 was directed to using an oil solution for free radical peroxide grafting the ethylene copolymer with maleic anhydride and then reaction with the polyamine. This concept had the advantage that by using oil, the entire reaction could be carried out in an oil solution to form an oil concentrate, which is the commercial form in which such additives are sold. This was an advantage over using a volatile solvent for the reactions, which has to be subsequently removed and replaced by oil to form a concentrate. Subsequently, in operating at higher polyamine levels in order to further increase the dispersing effect, increased problems occurred with the unreacted amine groups cross-linking and thereby causing viscosity increase of the oil concentrate during storage and subsequent formation of haze and in some instances gelling. Even though one or more moles of the ethylene polyamine was used per mole of maleic anhydride during imide formation, cross-linking became more of a problem as the nitrogen content of the polymers was increased. One solution was to use the polyamines and then to react the remaining primary amino groups with an acid anhydride, preferably acetic anhydride, of U.S. Pat. No. 4,137,185 or the sulfonic acid of U.S. Pat. No. 4,144,181. The cross-linking problem could also be minimized by avoidance of the ethylene polyamines and instead using amines having one primary group which would react with the maleic anhydride while the other amino groups would be tertiary groups which were substantially unreactive. Patents or published applications showing the use of such primary-tertiary amines noted above are U.S. Pat. No. 4,219,432, wherein a part of the polyamine was replaced with a primary-tertiary amine; U.S. Pat. No. 4,132,661; U.S. Pat. No. 4,160,739; U.S. Pat. No. 4,171,273; German No. P2753569.9; German No. 2,845,288; and French No. 2,423,530.
U.S. Pat. No. 4,516,104 and 4,632,769 represented a further improvement over the art in that they permitted the utilization of the generally less expensive polyamines having two primary amine groups, while achieving good dispersancy levels, inhibiting cross-linking and allowing initiator, e.g., peroxide, grafting in oil.
U.S. Pat. No. 4,517,104 discloses polymeric viscosity index (V.I.) improver-dispersant additives for petroleum oils, particularly lubricating oils, comprising a copolymer of ethylene with one or more C.sub.3 to C.sub.28 .alpha.-olefins, preferably propylene, which have been grafted with acid moieties, e.g., maleic anhydride, preferably using a free radical initiator in a solvent, preferably lubricating oil, and then reacted with a mixture of a carboxylic acid component, preferably an alkyl succinic anhydride, and a polyamine having two or more primary amine groups. Or the grafted polymer may be reacted with said acid component prereacted with said polyamine to form salts, amides, imides, etc. and then reacted with said grafted olefin polymer. These reactions can permit the incorporation of varnish inhibition and dispersancy into the ethylene copolymer while inhibiting cross-linking or gelling.
U.S. Pat. No. 4,632,769 discloses oil soluble viscosity improving ethylene copolymers such as copolymers of ethylene and propylene, reacted or grafted with ethylenically unsaturated carboxylic acid moieties, preferably maleic anhydride moieties, and then reacted with polyamines having two or more primary amine groups and a C.sub.22 to C.sub.28 olefin carboxylic acid component, preferably alkylene polyamine and alkenyl succinic anhydride, respectively. These reactions can permit the incorporation of varnish inhibition and dispersancy into the ethylene copolymer while inhibiting cross-linking or gelling.
There is, however, a need to provide multifunctional viscosity index (V.I.) improver additives which when added to oleaginous compositions such as lubricating oil compositions provide oil compositions which exhibit improved or better low temperature viscometric properties.
The problem of providing V.I. improving oil additives capable of providing oleaginous compositions exhibiting improved low temperature viscometric properties is addressed in U.S. Pat. No. 4,804,794 which discloses segmented copolymers of ethylene and at least one other .alpha.-olefin monomer, each copolymer being intramolecularly heterogeneous and intermolecularly homogeneous and at least one segment of the copolymer, constituting at least 10% of the copolymer's chain, being a crystallizable segment. These copolymers are disclosed as exhibiting good mechanical properties such as good shear stability and as being useful V.I. improvers which provide lubricating oils having highly desirable viscosity and pumpability properties at low temperatures. However, these copolymers are disclosed as being V.I. improvers, and there is no disclosure of grafting said copolymers with an ethylenically unsaturated grafting material or of grafting said copolymers and then reacting the grafted copolymer with a polyamine to produce a composition useful as a multifunctional viscosity index improver for oleaginous composition. Nor is there any disclosure in this patent of degrading these copolymers to reduce their molecular weight. It was heretofore generally believed that degrading these copolymers to obtain copolymers of lower molecular weight would generally adversely affect, i.e., broaden, their narrow molecular weight distribution and affect their intramolecular heterogeneity and intermolecular homogeneity. This, it was believed, would have a concomitant deleterious affect upon their ability to provide oil compositions exhibiting improved low temperature viscometric properties. It was further generally believed that these ethylene copolymers could not be grafted with conventional ethylenically unsaturated grafting materials or grafted with said grafting materials and thereafter reacted with a polyamine to form a multifunctional viscosity index improver without deleteriously or adversely affecting, i.e., broadening, their narrow molecular weight distribution (MWD) and affecting their intermolecular homogeneity and intramolecular homogeneity, thereby deleteriously and adversely affecting their property of providing oil compositions exhibiting improved low temperature viscometric properties. Indeed, degrading these copolymers to reduce their molecular weights broadens their narrow molecular weight distribution and affects their intramolecular heterogeneity and intermolecular homogeneity. However, it has surprisingly and unexpectedly been discovered that these degraded copolymers grafted with a grafting material such as carboxylic acid or anhydride and thereafter reacted with polyamine containing one primary amino group and at least one secondary amino group when added to oleaginous compositions provide oleaginous compositions exhibiting better low temperature viscometric properties than oleaginous compositions containing conventional non-narrow MWD ethylene-.alpha.-olefin copolymers, either degraded or undegraded, grafted with grafting materials such as carboxylic acid or anhydride and thereafter reacted with a polyamine.